The present invention relates to a CRT printing method and apparatus for making a print of a photographic scene with letters.
In recent years, there has been widespread use of various kinds of photographic prints of a scene with a season's greeting or complimentary phrase which are often used as postcards, greeting cards and the like. For making the prints, a CRT printing apparatus is heretofore used which is adapted to display on the screen of a CRT display device a scene image and a season's complimentary phrase as a composite image to which a photographic paper is exposed. The composite image is prepared by processing images of the scene from an image input device such as color TV cameras and the season's complimentary phrase graphically provided through a keyboard. For this image processing, the images are treated as video signals and processed with the aid of a computer.
Alternatively, there is also used a letter image printing unit comprising an illumination source and a lettered plate. This unit is adapted to be disposed in front of the CRT display device in such a way that the lettered plate is placed in contact with the photographic paper, thereby to print the image of the letters on, the photographic paper in contact printing simultaneous with the CRT image.
In any case, there is an essential requirement for these prints, that letters to be printed as a complimentary phrase on a photographic paper must be sharply outlined rather than degraded in image quality. This requirement is not fulfilled by the conventional CRT printing apparatus because the image of letter displayed on the CRT screen is unclear in outline. In addition to the lack of sharpness, the letters printed black are overlapped with transverse bright lines which result from rasters appearing on the CRT screen, thus degrading image quality.
Another problem with which the conventional CRT printing apparatus is that the color of letters to be printed depends on color filters used to print a color image from the CRT. Due to this dependency on the color filters, it is hard to print the desired color of letters on a color photographic paper.
Still another problem, in particular, of the letter printing unit is the necessity of an extra illumination source to illuminate the lettered plate. This necessity makes the unit complicated in construction and difficult to manufacture at a low cost.